1. Field of Invention
The present invention relates to the technical field of water treatment to inhibit the formation of scales. More particularly, the present invention relates to a pentaerythritol core, phosphonic acid terminated dendrimer and its preparation method, which is capable of inhibiting scales formation in industrial water systems, such as boiler, cooling, desalination, and oil production, especially in the industrial water treatment under the condition of high calcium concentration.
2. Description of Related Arts
Nowadays, water shortage and serious water pollution have become worldwide problems. Improving technical levels of industrial water treatment such as circulating cooling water, oilfield flooding and reverse osmosis has become an important measure for energy saving and emission reduction. Industrial water accounts for a proportion of over two thirds of city water consumption, and the circulating cooling water accounts for 70˜85% of the industrial water. Therefore, increasing cycles of concentration of industrial circulating cooling water has become an effective measure for conservation and protection of water resources. However, with the increase of the cycles of concentration in the circulating cooling water and calcium concentration, advanced requirement is put forward to antiscalants used for the circulating cooling water treatment, i.e., antiscalants should not only be capable of inhibiting scales but also have high calcium tolerance simultaneously.
With the increasing scarcity of freshwater resources, reverse osmosis water treatment, which is simple, efficient and economical, is increasingly applied to fields such as desalination of seawater and brackish water, preparation of ultrapure water and wastewater treatment, and has become the first selected technology and technical support for promoting virtuous cycle of water resource utilization. However, with the increase of reverse osmosis recovery ratio, the calcium concentration on the reject side of the membrane is gradually increasing, and especially in seawater or brackish water, the calcium concentration is higher, which requires the antiscalants to have excellent inhibiting scale performance under high calcium concentration, i.e., the antiscalants should have higher calcium tolerance.
TABLE 1Commercially available amino methylene phosphonatesApplicatingStructure and MolecularName (Abbreviation)ageweightAmino trimethylene phosphonic acid (ATMP)1970s   Mw: 299 Ethylene diamine tetra(methylenephosphonic acid) (EDTMP)1970s   Mw: 436 Diethylenetriamine penta(methylenephosphonic acid) (DTPMP)1970s   Mw: 573 Hexamethylene diamine tetra(methylenephosphonic acid) (HDTMP)1980s   Mw: 492 Polyamino polyether tetra(methylene phosphonate) (PAPEMP)1990s   n: 2~3 Mw: 600
There are two series in the conventional scale antiscalants, phosphonates and carboxylate polymers. For having good efficiency of corrosion and scale inhibition, phosphonates has been widely applied. Besides 1-Hydroxyethylidene-1,1-diphosphonic (HEDP) and 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA), the phosphonates currently available on the market mainly belongs to amino methylene phosphonic acid, which is shown in table 1.
Except that the PAPEMP is oligomer, the phosphonates based methylene phosphonic acid all belong to micromolecular compounds. Due to low price and good inhibition scale efficiency thereof, they are widely applied to industrial water treatment, and occupy a great market share therein. However, almost all of the micromolecular phosphonates has no satisfying calcium tolerance.
Compared with other micromolecular phosphonates based methylene phosphonic acid such as ATMP, EDTMP, DTPMP and HTDMP, PAPEMP belongs to polymer and has a higher molecular weight. U.S. Pat. Nos. 5,535,157 and 5,358,642 disclose that PAPEMP has high calcium tolerance and is suitable for harsh conditions of high hardness water. However, PAPEMP has far less inhibition scale efficiency than micromolecular phosphonates under conditions of low calcium concentration, and requires a higher concentration of antiscalants for the same inhibition scale effect. Meanwhile, PAPEMP has bad inhibition scale efficiency to barium sulfate and is not suitable for scale inhibition treatment on oilfield flooding and reverse osmosis water.
Compared with linear polymers, dendrimer, which is a new type polymer in recent years, has structural characteristics of accurate molecular structure, high geometric symmetry, a great quantity of functional groups in periphery, cavity existed in the molecule, controllability of molecular weight and nanometer-sized molecule and etc. Therefore, the dendrimer draws universal concern of more and more scientists from all over the world and has important application prospects in many areas such as industry, agriculture, national defense, biomedicine, delivery material and catalysis.
The pentaerythritol core, phosphonic acid terminated dendrimers prepared by the present invention are new structure, and not disclosed both in China and other countries. Experimental results show that the new type dendrimer has high calcium tolerance, and excellent inhibiting scale performances for calcium carbonate, calcium sulfate and barium sulfate.